The invention relates to a high-pressure discharge lamp comprising a discharge envelope which accommodates an ionizable filling and two main electrodes, between which a discharge path extends, this discharge envelope having a wall of ceramic translucent material consisting mainly of densely sintered polycrystalline yttrium aluminium garnet, and to a method of manufacturing a high-pressure discharge lamp provided with a discharge envelope having a wall of such a material.
U.S. Pat. No. 3,767,745 discloses a high-pressure discharge lamp provided with a discharge envelope having a wall of translucent densely sintered polycrystalline yttrium aluminium garnet (yag). In the known lamp, the material of the wall of the discharge envelope is obtained by hot pressing. In this method, a starting material is sintered at a high temperature and at high pressure. A disadvantage of the method used is that it requires complicated apparatus. A very great disadvantage is that with the known method only tubular bodies, such as discharge envelopes, can be obtained, whose density is considerably less than 100% of the theoretical density. The translucence is determined to a great extend by the density and will be at an optimum with a density of 100%. Densities which are less than 98% of the theoretical density in practice lead to such a low translucence that a practical use as material for the wall of a discharge envelope is excluded.